Because of the demands placed on the automotive industry by government fuel economy and exhaust emissions standards, fuel injection systems for internal combustion engines have, in recent years, overtaken standard carburetion as the means for providing a measured charge of suitable fuel and air mixtures to the combustion chamber of an internal combustion engine. Normally aspirated internal combustion engines mix the fuel and air required to create a suitable combustion mix in a carburetor. The combined fuel and air mixture is then drawn into the combustion chamber of the internal combustion engine by the normal operating vacuum of the engine. In fuel-injected engines, fuel and air are separately delivered to the engine combustion chamber. A precisely metered amount of fuel is "injected" into the intake manifold in the form of an atomized fuel charge. The advantages gained by the use of fuel injection include improved performance and fuel economy. By virtue of sophisticated micro computers, the amount of fuel which is to be injected into each cylinder can be precisely adjusted based on a wide variety of external conditions, including outside air temperature, engine temperature, humidity levels, atmospheric pressure and exhaust content. In modern fuel-injected engines, a central electronic control unit monitors these, and other factors, and regulates the performance of the overall fuel injection system based thereon.
Successful operation of fuel-injected engines, however, requires optimized performance from each individual electronically operated fuel injector. Degradation in the performance of any individual fuel injector, however, is extremely difficult to monitor while the vehicle is actually in operation. While test equipment has been devised to monitor the operation of electronic fuel injectors in an automotive garage environment, means to test fuel injectors under actual operating conditions have heretofore been unduly complex and expensive.
The problem of testing individual cylinder performance based on selective operation of fuel injectors is compounded by the adoption of multi-port fuel injection systems in modern automotive engines. Multi-port fuel injection involves a simultaneous operation of a group of fuel injectors under a single command from the motor vehicle electronic control unit. Accordingly, it is difficult to control, electronically, the electronic control unit itself on a selective basis, without disabling an entire group of fuel injectors simultaneously. Sequential port fuel injection, on the other hand, involves selective operation by the electronic control unit of individual fuel injectors. However, this sequential operation of fuel injectors is controlled by a pre-programmed series of instructions contained within the electronic control unit itself, again making it impossible to instruct the electronic control unit to selectively operate only a single fuel injector on demand.
The technique of individual operation of fuel injectors for testing purposes is taught by Kaireit, in U.S. Pat. No. 3,919,885. Kaireit teaches the individual, selective operation of fuel injectors. However, in order to determine fuel injector operation, it is necessary to visualize the output of the fuel injector, as taught by Kaireit. Of course, such visualization is impossible when a vehicle is in operation.
Blanke, in U.S. Pat. No. 4,841,765, teaches the manual disablement of individual fuel injectors by disconnecting the electrical wire leading to the fuel injector, or by disconnecting the fuel line leading to the fuel injector. Again, this methodology is unsuitable for use while the vehicle is in actual operation. Devices to measure the volume of fuel utilized by fuel injectors are taught by Takahashi et al, in U.S. Pat. No. 4,798,084, and the monitoring of the operation of fuel injectors while the vehicle is in motion is taught by Krohn et al, in U.S. Pat. No. 3,875,792.
None of these apparatus or method patents, however, provide the necessary improvements to allow selective electronic disabling of the fuel injectors while the vehicle is in motion, and all require the installation of substantial and sophisticated test consoles, interposed between the various engine sensors and the test equipment.
The present invention comprises a simple apparatus for individually disabling electronic fuel injectors in an internal combustion engine, allowing the vehicle fuel injection system to be tested while the vehicle is in normal operation.